CMA-676, a conjugate composed of an engineered human anti-DC33 antibody linked to a potent anti-tumor antibiotic, calicheamicin, provides a new method of drug delivery by utilizing a monoclonal antibody to target leukemic cells. Although the current chemotherapeutic approaches result in complete remission (CR) rates as high as 80% in the younger adult AML population, the elderly population raises therapeutic problems since the intensive chemotherapy generally used in younger patients is very toxic in the elderly. Since CMA-676 has a low toxicity profile, it is envisioned that it will be particularly useful in treating elderly patients in relapse who have a poor tolerance for standard cytotoxic chemotherapy regimens.